If you participated in TEDx , what would you talk about?
For a serious discussion, remember to pay attention to spelling and proper grammar. You also need to avoid slangy, childish forms such as "u" for you and multiple punctuation ("?!" makes me think that you are waving your arms and yelling). It's hard to take a messy sentence seriously.
For my own topic, I'd probably talk about something on the physics or mathematics of music. That's what currently comes to mind.
thank you for your notice :)